The present invention relates to a method and apparatus for a cleaning treatment in a system, in which, for example, substrates used for a liquid crystal display (hereafter referred to as LCD) and a semiconductor device are treated.
Recently, it has become an urgent need in apparatuses for various kinds treatment, for example in a resist coater which is used to form a resist film on a LCD substrate, that the size of an apparatus itself is reduced, the production cost is decreased and in addition a running cost of the apparatus is decreased.
In a resist coater generally used in a fabrication process of LCD, treatments of resist coating and cleaning are given on a glass substrate (an object to be treated), and there are two kinds of resist coater, which are of types of spin-coating and spray-coating.
A resist coater of a spin-coating type comprises, for example: a spin chuck, on which a glass substrate is mounted, and which is free to be shiftable vertically while being free to be rotatable; a resist solution instillator which supplies a resist liquid in the middle potion of the substrate drop by drop; a jet nozzle of a cleaning liquid to clean the surface of the substrate; and a rotary cup and a drainage cup being disposed outside the substrate in a manner doubly surrounding the substrate, wherein the rotary cup is inside the stationary cup and the rotary cup receives the resist liquid or a thinner flowing out or flying out from the substrate.
In such a resist coater, a glass substrate is mounted on a spin chuck which is free to be shiftable vertically while being free to be rotatable and a resist liquid is supplied to the middle portion of the substrate drop by drop while rotating the substrate to form a uniform resist film by a centrifugal force. In the case, a residue of the resist liquid which flows out or flies out from the substrate is received by the rotary cup to be discharged. In a following step, a height of the spin chuck is changed and a cleaning liquid is supplied from the cleaning liquid jet nozzle to the edge of the substrate to clean the edge portion of both surfaces of the substrate and a waste liquid is received by the drainage cup to be discharged. As a cleaning liquid, a solvent such as a thinner is used, since it is less in pollution and higher in safety.
In the same resist coater, since a used cleaning liquid (a waste liquid) has a lot of a resist ingredient dissolved therein, the used cleaning liquid cannot be reused on the substrate and is stored in a waste liquid storage unit through a waste liquid pipe. The waste liquid stored in the storage unit is wasted when it is accumulated to some extent.
In the drainage cup, since a thinner constantly including a resist ingredient is fed, the resist ingredient is piled up as a deposit on the inner wall of the cup in a adhered manner. When the resist ingredient is adhered and piled up to some extent, clogging will be caused, the inner wall of the drainage cup has been conventionally cleaned at an interval and the deposit has been separated off. Such a situation is also applied to the case of the rotary cup which directly receive the used resist liquid itself.
However, in a conventional resist coater, a thinner is sprayed toward the inner surface of a cup from a nozzle exclusively used for cleaning the inside of the cup disposed in the cup in order to remove the deposit inside the cup and therefore a lot of the thinner is required.
As described above, there has been a problem in a conventional resist coater, which is an apparatus for a coating treatment, that contamination such as an resist is adhered on the inner wall of a cup when the treatment is repeated and such contamination requires a lot of the thinner to be removed, so that the expense for cleaning is accumulated.
Besides, a used cleaning liquid cannot be used in a cleaning treatment of a glass substrate to be cleaned and therefore the used cleaning liquid is wasted as a waste liquid, which has been another cause to increase a running cost.
While application of a resist liquid on the surface of an object to be treated such as a LCD substrate has been effected by a spin coating method, In the case, since a LCD substrate has a rectangular shape, which causes a turbulent flow in the air by rotation, there arises a problem that uniformity of a thickness of a resist film cannot be maintained.
For such a reason, conventionally a surrounding space above, under and near the sides of a spin chuck as a holding means for holding LCD substrate and a LCD substrate are enclosed by a rotary cup with a cover and a rectifying plate is disposed above the LCD substrate in the rotary cup with a cover and the air supplied through an air supply port formed in the cover of the rotary cup with a cover is rectified by the rectifying plate to be discharged through an exhaust port located at the bottom of the rotary cup. In such a manner, A disorder in thickness of a resist film by a turbulence in the air have been avoided. A stationary cup is so disposed as to enclose the side and lower portions of the covered cup in order to prevent an air stream created by rotation of the rotary cup from flowing back into the inside of the rotary cup.
However, in a resist coater in which a resist liquid is applied by a spin coating method of this kind, a resist solution is sprayed outwardly by an centrifugal force and therefore a resist is adhered on the inner side and the bottom of the rotary cup, back surface of the covered cup, and the lower surface of the rectifying plate and the like. Besides, there is a fear that the resist is adhered in the inner side and the bottom of the stationary cup. In such a manner, a resist adhered on the rotary cup, the inside of the stationary cup, on the cover, the rectifying plate and the like is dried to produce particles. If the particles are adhered on a LCD substrate, a difficulty occurs on a circuit patterning and the like and at the same time a problem of reduction in a yield is resulted.